Effacement is the thinning (sometimes called ripening) of the cervix in preparation for delivery. During effacement, the cervix goes from more than an inch thick to paper thin.
Found on http://www.encyclo.co.uk/local/20415

This is the thinning and shortening (sometimes called 'ripening') of the cervix during early labour. During effacement, the cervix goes from more than an inch thick to paper thin.Found on http://www.encyclo.co.uk/local/20423

(ә-fās´mәnt) the obliteration of form or features; said of the cervix uteri during labor when it shortens from 1 or 2 cm in length to paper thin and there is no longer a cervical canal but only an external cervical os.Found on http://www.encyclo.co.uk/local/21001

[histology] Effacement is the shortening, or thinning, of a tissue. It can refer to cervical effacement. It can also refer to a process occurring in podocytes, for example in minimal change disease. In histopathology, it refers to the near obliteration of a tissue, as in the normal parenchyma of tissues in the case of some cancers. ...Found on http://en.wikipedia.org/wiki/Effacement_(histology)

The thinning and shortening of the cervix that is necessary to prepare for a vaginal delivery. Effacement occurs during the first stage of labor . Effacement is measured in percentages from 0 - 100%, with 100% being fully effaced.Found on http://www.pregnology.com/AZ/E/1